[XRay][clang] Remove dependency on libatomic for XRay builds
[XRay][clang] Remove dependency on libatomic for XRay builds

Summary:
This change depends on D31381 where we change the implementation to use
sanitizer_common provided atomic operations library.

Fixes http://llvm.org/PR32274.

Reviewers: pelikan, dblaikie

Subscribers: cfe-commits

Differential Revision: https://reviews.llvm.org/D31382

git-svn-id: ffe668792ed300d6c2daa1f6eba2e0aa28d7ec6c@298835 91177308-0d34-0410-b5e6-96231b3b80d8

apple/swift-clang,llvm-mirror/clang,llvm-mirror/clang,llvm-mirror/clang,apple/swift-clang,apple/swift-clang,llvm-mirror/clang,apple/swift-clang,llvm-mirror/clang,llvm-mirror/clang,apple/swift-clang,apple/swift-clang,apple/swift-clang,apple/swift-clang,apple/swift-clang,llvm-mirror/clang,apple/swift-clang,llvm-mirror/clang,llvm-mirror/clang,llvm-mirror/clang